The notebooks used by Fred Sanger, Britain's most decorated scientist, to record experiments that won him two Nobel prizes have been saved for the nation.

The Wellcome Trust has stepped in to take possession of the books in which Sanger noted down the progress of research that led to his winning a chemistry Nobel prize in 1958 and a second in 1980, a chemistry double that has never been matched.

The 35 beige books - with yellowing pages and Sanger's careful blue-ink handwriting - give crucial insights into his thinking as he carried out work that transformed medical science, first by unravelling the structure of a protein, insulin, and later by working out the DNA of a living being, in this case a virus. Both were scientific firsts. The DNA techniques of Sanger - who will be 89 a week tomorrow - are now used by gene sequencers throughout the world. If his books were sold on the open market, they would be worth millions.

'Sanger was the father of genome sequencing,' said Clare Matterson of the Wellcome Trust. 'With his notebooks, we now have a clear record of his influences and thought processes. It would have been tragic if these notebooks had ended up outside Britain.'

After collating the entries of the notebooks, given by Sanger to the trust, the organisation will make them available for study to the public at the Wellcome Library in London. 'This will give insight into the thinking of one of our greatest scientists,' added Matterson.

No other researcher from the UK has won more than a single Nobel prize. Apart from Sanger, the only others were Polish-French scientist Marie Curie and American physicist John Bardeen. Both are venerated in their native countries, but Sanger is hardly known here, partly because of his intense modesty.

'I was just a chap who messed about in a lab,' he said last week at the Cambridgeshire home he shares with his wife, Margaret.

Sanger is summed up by the biographer Georgina Ferry. 'Small, self-effacing and modest in the extreme, Sanger had determination, perseverance and the scientific equivalent of green fingers for developing new lab techniques and getting them to work. He was the kind of scientist who thinks with his hands.'

Sanger was born in Rendcomb in Gloucestershire. His father was a doctor and his mother the daughter of a wealthy cotton manufacturer. 'I took up biology partly due to my father's interest in the field. But I never wanted to do anything except research. I hated lecturing and was only happy at the lab bench.'

More than 20 years after his retirement, Sanger's green fingers continue to work their magic. His Nobel prize cash was used to buy a house that came with several acres of land. For two decades, Sanger has laboured to transform this into a large, lavish walled garden filled with ornamental poppies, lilies, roses, acanthuses and fruit trees.

'I gave up science 20 years ago,' said Sanger who, although now slightly stooped, remains alert and focused. 'I was happy to. I had no more ideas. I have my time on my garden since then.'

Almost his only public utterance in two decades was to put his name to a letter by other UK Nobel laureates protesting about the Iraq war.

'I was raised as a Quaker,' he said. 'I learned to abhor violence. During the war I was a conscientious objector and I still hate war. That is why I signed that letter.'